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Family trees: The social life of plants

PITY the poor Christmas tree! Cut down as a mere youngster and taken away from family and friends to be dumped in stifling warmth, daubed with ridiculous baubles and left to a lonely, lingering death. OK, so maybe that’s pushing the anthropomorphism too far. Of course trees don’t feel sadness, indignity or pain, but neither should we think of them as dumb lumps of lignin and chlorophyll. It is becoming clear that plants have much richer social relationships than anyone imagined. Many are in contact with one another by direct line or mysterious underground signals. Others recognise and tolerate neighbours. Some are even generous and self-sacrificing towards their kin.

One of the foundations of any relationship is communication. In the 1980s, when plant biologists first proposed the phenomenon of “talking trees”, it was controversial. Today everyone accepts that many plant species release volatile chemicals into the air when they are attacked by herbivores, and that these chemicals are detected by other plants, which then prepare for the threat. What’s still unclear is whether these interactions constitute two-way communication. Plants may have no choice but to emit volatiles when their leaves are damaged, and once broadcast, the signals are undirected and available to anyone. So it is far from clear that these are messages intended to warn other plants. Recently, however, a more convincing form of plant communication has come to light.

Some plants reproduce by throwing off plantlets and stay connected to these offspring with horizontal stems above or below ground. Strawberries form such networks, as do bracken, clover, buttercups, reeds and bamboo. “In temperate ecosystems, 50 …